Topology Configurations for Multi-Cell Routing

In a multi-cell situation you have two topology options for configuring multi-cell routing preference rules for applications that exist in two cells, which we consider to be recommended best
practices. Neither of these topologies employ core-group bridges
and for Versions 7.x and higher it is discouraged to use core-group
bridges to link cells.

Star Topology

The Star Topology works well if you have multiple cells and the center cell contains all on demand
routers (ODR's). You would remove all ODRs from the point cells and move them into the center cell. For the sake of high availability it's a good idea to cluster the ODRs, and to keep them on separate hardware and separate power supplies, etc. You would use the linkcells script to link the cells. This is easy, it's quick, and it's a best practice.
It's highly-scalable, as we can add more cells as necessary. Discovery
is also still there -- if you add applications to one cell or another, the ODR will learn of them automatically, just as if everything were in one cell.

Indications for the star topology include:

For the consolidation of ODRs, ODRs in a single center cell can route to application servers in multiple point cells.

Multiple cells share the same hardware resources. A single Application Placement Controller (APC) in the center cell can manage the performance of all cells in the star topology by starting and stopping application servers in point cells to meet current demand.

For scalability, if a single cell is preferred from a management perspective, there are scalability limitations associated with a single cell. This multi-cell topology enables you to scale higher while
still managing a single cell of ODRs, and at the same time, also managing
dynamic clusters across all cells as a unit.

Peer-Cell Topology

The Peer-cell
Topology works well if you have two or more disjoint data centers, one cell per data center, and you want failover capability
between them. In this topology, the ODRs remain in the cells; however, the two cells are not joined via core-group bridges. In front
of the two cells, you have one or more load-balancers, plugins, or sprayers which are able to both preserve session affinity (as applicable), as well as equitably distribute traffic.